When she incurs Neptune's wrath by finding a diamond ring buried under rocks in the ocean, Emily is put under a curse that will force her to choose to be either a mermaid or a human and split up her parents forever.

When Neptune tells Emily and her merman father and human mother to return to Brightport to try to make merpeople and humans work more closely together, Emily faces problems with old enemies, her new, half-merfolk friend Aaron, and a mystery related to a group of legendary lost sirens.

Emily is headed to a tropical island for a relaxing vacation with friends and family. And this time, Emily promises her best friend, Shona, there will be absolutely no adventure just plenty of fun. But somehow excitement always seems to find Emily, and before she knows it, she ends up on the other side of a powerful waterfall on a forgotten island no one else can get to.

"Traveling home by cruise ship should be a relaxing break after Emily's latest adventure, but things take a turn when the ship is overtaken by a pirate king and his crew. After the pirates collect everyone's riches, they steal something even more valuable: Aaron. The pirate king's eldest son takes Aaron captive, forcing him to help guide the pirates to the mythical Trident's Treasure. So Emily dives into action and joins the younger son's crew in...

When Emily makes a wish on a magic stone, she gets a glimpse of what the future holds--and it's a disaster! She tries to make things right, but each trip through time takes Emily to a future where things turn out badly for either the humans of Brightport or the merpeople of Shiprock. Plastic pollutes the ocean, garbage overflows the landfills, and the two towns are no longer getting along. Emily realizes she can't save her hometown and the ocean alone,...